[GuRLCrUMbS01]

the substances:
oxalic acid
benzoic acid
citric acid
salicylic acid
urea

Questions:
1) Which of the following has the highest melting point? how would you account for this?(discuss of Van der Waals interaction and Hydrogen bonding)

2)compare their intermolecular forces

can you guys please help me?

[GuRLCrUMbS01]

okay.


1) The one with the highest melting point is urea which is 189 degrees Celsius. (i dont know how to discuss it on account of van der waals and hydrogen bonding though)

2) this one I dont know. I dont know how to comprae their intermolecular forces but i get the definition

there simple no helping to it. i need help  cuz i dont know how to answer it

[jholthus]

Both basically are asking you to look at how things are bonded/in space so look at them and determine what might cause the melting points to be higher.

For number two it is kind of asking the same thing as far as how things are bonded together... dispersion, H-bonding, dipole-dipole moments.

I don't really know how else I could explain it without giving answers away. Just try to reference those points in your answer

[Arkcon]

What is melting?  What does it mean?  Really think about it.  You have a solid, rigid, made of molecules repeating one after another, locked together ... somehow.  Then you melt it, they ignore what was once holding them together and slide past each other, why do that happen sooner for some?  Try drawing a pair of the same molecule side by side, and see if you can figure it out.

[GuRLCrUMbS01]

i dont get what you guys are saying at all to be honest but thanks anyway

[fledarmus]

Start with some low level definitions then. Draw the structures of your molecules. Then consider, what IS hydrogen bonding? Which of your molecules might be able to interact through hydrogen bonding? What would make those interactions stronger or weaker? What are Van Der Waals forces? What makes them stronger or weaker?

If there were no forces holding two molecules together in a solid, entropy would ensure that they were as far away as possible, in a gas. The stronger the forces holding them together, the higher the temperature has to be to drive them apart, and the higher the melting point of the solid. You need to look at the structures of your molecules, and see which of them would be the most likely to have strong forces holding the molecules together.